in armpits are because of severe uncontrolled diabetes
These boils can not be cancer,as in that case these anti diabetic medicines would not have resulted in disappearance of the boils.If these boils become all right with these anti diabetic drugs,this in itself confirms that it is not due o cancer.
As far as her drowsiness
on taking these medicines is concerned,it can be due to low levels of blood sugar or low levels of blood pressure.
Next time whenever your mother becomes drowsy after the medicines get her blood sugar levels and blood pressure measurement done.
If any thing found low,it can be corrected by adjusting he dose of medicines.